Not Just Cucumbers: The Most Effective Blo.od Sugar–Lowering Food Is a Familiar Staple at the Dinner Table

Not only cucumbers or bitter melon—one familiar food found in everyday meals is now considered the most effective “weapon” for lowering blood sugar. Inexpensive, easy to prepare, yet often overlooked, this ingredient is being highly valued by experts.

Recently, natural foods that help lower blood sugar have attracted growing attention, especially as rates of prediabetes and type 2 diabetes continue to rise. Among commonly mentioned foods, cucumbers rank third, bitter melon second, while the top spot belongs to a very familiar ingredient in Vietnamese kitchens: onions.

Unassuming and rarely labeled a “superfood,” onions have long been treated as a secondary ingredient in stir-fries and soups. However, modern nutrition research shows that this inexpensive bulb has a clear impact on blood sugar control and is even described as a form of “natural insulin.”

According to Western medical literature, onions are rich in quercetin, a powerful antioxidant flavonoid that helps improve insulin sensitivity. In addition, sulfur compounds in onions have been shown to reduce fasting blood glucose and help lower HbA1c (glycated hemoglobin)—a key indicator of average blood sugar levels over the past 2–3 months.

Associate Professor Dr. Nguyễn Thị Lệ Thu, a nutrition and endocrinology specialist at Hanoi Medical University, notes:
“For people with prediabetes or newly diagnosed type 2 diabetes, adding onions to daily meals may help improve insulin response. However, this effect only works alongside a balanced diet and regular physical activity; onions should not be considered a medical treatment.”

Meanwhile, cucumbers and bitter melon still play certain roles. Cucumbers are high in water and low in calories, helping slow sugar absorption after meals. Bitter melon contains charantin and polypeptide-P, compounds proven to lower blood sugar. However, in terms of availability, long-term use, and overall impact, onions are considered more effective.

Another often-overlooked factor in blood sugar control is lifestyle during colder seasons. As temperatures drop, many people become less active, reducing basal metabolic rate and increasing insulin resistance. Experts recommend maintaining the habit of walking for 20–30 minutes after meals—even indoors—as light activity has been shown to significantly reduce post-meal blood sugar spikes.

Many people also mistakenly believe that completely eliminating carbohydrates is the best way to control blood sugar. In reality, a very low-carb diet over a long period can lead to muscle loss, reduced basal metabolism, and even faster decline in pancreatic function.

Instead, experts recommend focusing on portion control rather than food elimination. Carbohydrates should still be consumed, prioritizing whole grains, controlling serving sizes, and balancing them with vegetables and high-quality protein. For example: oatmeal with eggs for breakfast; half a bowl of brown rice with tofu or steamed fish for lunch; and a light dinner with whole-grain porridge and sautéed or boiled onions.

Onions can be prepared in many ways: quickly sautéed with olive oil, added to salads, cooked in soups, or eaten with porridge. When cooked at moderate temperatures, onions retain beneficial bioactive compounds that help stabilize blood sugar.

Experts also emphasize that no food can replace medication; dietary approaches are supportive measures only. However, for a specific group—those in the prediabetes stage (fasting blood glucose 6.1–7.0 mmol/L or impaired glucose tolerance)—diet and lifestyle changes can make a significant difference.

“This is a golden window for intervention,” Dr. Thu stresses. “With proper dietary adjustments, increased physical activity, and stable weight maintenance, many people can keep their blood sugar at safe levels for a long time without medication.”

From a humble kitchen ingredient, onions are gradually being recognized for their true value. In the journey of blood sugar control, the most effective solutions sometimes come from the most familiar foods—when they are understood and used correctly.